Conventional telecommunications networks typically comprise two distinct communication pathways or sub-networks—a voice network and a signaling network. These two networks function cooperatively to facilitate calls between users. The voice network is responsible for the transmission of voice (or user data) while the signaling network has a number of responsibilities. These include call setup, call teardown, and database access features.
In simple terms, the signaling network facilitates the dynamic linking together of discrete voice-type communication circuits so that a voice-type connection can be established between two parties. These functions are referred to as call setup and call teardown. The signaling network also provides a framework through which non-voice related information can be transported. This data and transport functionality, however, is transparent to the users. This signaling technique is often referred to as out-of-band signaling where the term “band” indicates the voice band. Examples of non-voice data transport include 800 number database access, calling card verification services, and caller ID services.
In order to ensure consistent and reliable communication across the signaling network infrastructure, a common or standard digital signaling protocol was established by the International Telecommunications Union (ITU) in the mid 1960's. This protocol was known as Signaling System 6 (SS6) and has since evolved into the slightly more sophisticated SS7 currently in use.
As a protocol, SS7 defines the hierarchy or structure of the information contained within a message or data packet. This internal data structure is often referred to as the protocol stack, which is comprised of a number of well defined strata or layers. In general terms, the SS7 protocol stack consists of 4 levels or layers: the physical layer, the data link layer, the network layer, and the user part layer. It will be appreciated that communication networks operating outside of the United States often refer to the SS7 protocol and network as Common Channel Signaling # 7 (CCS#7). For simplicity, the term SS7 is used herein. However, it is understood that embodiments of the present invention can be used equally in CCS7 or SS7 networks.
An SS7 network includes a plurality of SS7 nodes, commonly referred to as signaling points (SPs), which include service switching points (SSPs), signal transfer points (STPs) and service control points (SCPs).
An SSP is typically installed in tandem or Class 5 offices and is capable of handling both in-band signaling and SS7 signaling. An SSP might be a customer switch, an end-office, an access tandem and/or a tandem.
An STP transfers signaling messages from one signaling link to another. STPs are packet switches and are generally installed as mated pairs, each mate of the pair being located remotely from the other to ensure redundancy and reliability in the event one is damaged, for example by a natural disaster, as well as load sharing. Thus, for example, one STP of the pair might be located in North Carolina while the other of the pair is located in Illinois, each one typically operating nominally at no more than 40% of its maximum processing capacity.
Finally, SCPs control access to databases such as 800 number translation, 800 number carrier identification, credit card verification and the like. SCPs may include a front-end computer that received database queries from SS7 SPs and provides responses to the queries.
Each of the SP's above is interconnected using SS7 signaling links. Signaling links are transmission facilities used to connect SPs together. Conventional SS7 signaling links are dedicated, bidirectional facilities operating at a fixed-bandwidth, for example 56 kbps in the United States and Canada, and 64 kbps when clear channel capability is required. Every link will typically have a mate for redundancy and enhanced network integrity.
Dedicated SS7 links that connect an STP to other SPs within an SS7 network can be capital intensive and expensive to maintain. Moreover, because redundant SS7 data links are typically used, their maintenance adds to the capital intensity and expense.
These expenses create a formidable barrier to further expansion of wired telephone networks as well as cellular telephone networks. Consider, for example, a telecommunications carrier or service provider that desires to enter a market and provide telephone service to customers. The provider must be connected to both the signaling and voice networks.
With regard to the signaling network, the necessary connectivity involves establishing at least one communication link between an end office, or SSP, and a pair of STPs. This task can be accomplished through the use of an intermediate, non-intelligent multiplexing node; that is, the node cannot discriminate information, but merely passes it. Such multiplexing nodes concentrate information onto and distribute information off of the SS7 physical link(s).
Accordingly, in order for an SSP to connect to the signaling network, dedicated physical SS7 links (expensive communication grade cables) must be run between the associated multiplexer and each remotely located STP. The new or expanding provider can either install new cables, or lease a predetermined, fixed-bandwidth on existing lines from a network service provider. Moreover, the provider must lease the maximum bandwidth which would otherwise be required during peak calling periods, regardless of how small the bandwidth needed during normal calling periods.
Similarly, when a cellular service provider enters a new geographic area or market, the cellular service provider must connect the elements of the cellular radiotelephone network to the wired telephone network using SS7 links.
In any case, such dedicated SS7 links are typically very expensive, whether installing or leasing, and can represent a recurring cost of as much as $10,000 per month. Such high costs present a problem for existing carriers and service providers, as well as for new carriers and service providers looking to enter the marketplace. The large number of SS7 links that must be provided can thus increase the expansion or introduction costs for wired and wireless networks, thereby increasing consumer cost and/or reducing consumer access to competitive service providers.
One scenario in which providing dedicated, fixed-bandwidth SS7 links is particularly inefficient is connecting telephone end offices in sparsely-populated areas to an STP. For example, referring to FIG. 1, SSPs 100, 102, and 104 may be located in a sparsely-populated area remote from an STP. Hence, the SS7 signaling bandwidth requirements to and from each SSP is small, i.e., requiring only a fraction of the 56 kbps provided by a conventional SS7 link. However, in conventional SS7 networks, each SSP 100, 102, and 104 is required to connect to STP 106 through fixed-bandwidth SS7 access links 108, 110, and 112.
Even though SSPs 100, 102, and 104 use only a fraction of the bandwidth provided by access links 108, 110, and 112, the owners of SSPs 100, 102, and 104 are required to pay for the full amount of bandwidth provided by access links 108, 110, and 112. Hence, providing SS7 signaling services to end offices in sparsely populated areas is not cost effective using conventional fixed-bandwidth SS7 links. The cost is further increased if the fixed-bandwidth links span long geographic distances.
Another configuration in which using conventional fixed-bandwidth SS7 links is inefficient is in mesh networks used to connect end offices. Referring to FIG. 2, each of the SSPs 200-208 is connected to all of the other SSPs using fixed-bandwidth SS7 links 210. Such a configuration is commonly used in European countries. In a mesh network with n SSPs, n fixed-bandwidth links must be added to the network for each additional SSP added to the network. For example, in FIG. 2, there are five SSPs. In order to add a sixth SSP, five fixed-bandwidth SS7 signaling links are required to connect a sixth SSP to each existing SSP in the network. In order to add a seventh SSP to a mesh network of six SSPs, six additional fixed-bandwidth links are required. Such a scheme can make adding new SSPs to a mesh network cost-prohibitive due to the cost of each fixed-bandwidth link.
Accordingly, there exists a need for novel methods and systems for interconnecting SS7 SPs that reduces the number of fixed-bandwidth SS7 links.